Infection with Vibrio cholerae elicits protection against subsequent disease for three to ten years. Immunity against V. cholerae is serogroup specific. A major protective antigen of this organism and many other bacterial pathogens is the 0-specific polysaccharide (OSP) of lipopolysaccharide (LPS) (Passwell et al., Infection Immunity 2001; 69(3):1351-7; Robbins et al., Pure Appl Chem. 1999; 71:745-54). Unfortunately, polysaccharides are poor immunogens, likely due to the lack of T cell help, especially in young children. Conjugation of polysaccharides to proteins can markedly improve their immunogenicity, including magnitude, type, and duration (Goldblatt, Clinical and Experimental Immunology 2000; 119(1):1-3); examples include pneumococcal, meningococcal, and Haemophilus influenzae b conjugate vaccines (Claesson et al., Ped Inf Dis J 1991; 10(8):560-4). Current oral cholera vaccines provide lower level and shorter term protection than that afforded by wild type infection. The oral killed-cholera vaccine, WC-rBS (Dukoral), does not elicit memory B-cell responses to LPS (Alam et al., Clin Vaccine Immunol; 18(5):844-50). In addition, children had a lessened response to LPS after wild type disease and vaccination (Chowdhury et al., Pediatric Infectious Disease Journal 2008; 27(11):986-92).
Conventional conjugation techniques, such as conjugate vaccine production techniques, are limited in that they can be slow, costly, inefficient, require use of exogenous or added chemical linkers, and/or can lack reproducibility. Improved techniques are required.